Train from Venice to Munich

Check the number of stops, as many have reported not being able to sleep through those interruptions. Also, hopefully there are no train changes.
Also, if you're staying at a vacation home type rental, as you won't be able to drop off your luggage at 6:00am.
I'm sure many here with have direct experiences with sleeper trains. Good luck!

https://search.ricksteves.com/?button=&date_range=2y&filter=Travel+Forum&query=Sleeper+trains&utf8=%E2%9C%93

Perhaps some useful info in the above Search.

I’ve taken approximately 17 over night trains and rented a sleeper car each time and was able to sleep on all except from Rome to Taormina because that ride was bumpy. You must sleep somewhere so why not kill two birds with one stone. Furthermore, trains consume less energy and can run on electricity making it a much better option than a fuel guzzling airplane.

The NightJet makes the following stop after departing from Venice at 9:05 PM:

9:17 PM Venezia Mestre
9:38 PM Treviso Centrale
9:56 PM Conegliano
10:14 Pordenone
10:47 PM Udine
12:05 AM Tarvisio Boscoverde
12:45 AM Villach Hbf
2:20 AM Bischofshofen
4:05 AM Salzburg Hbf
(no stop?) Rosenheim
5:52 AM Munich

There's a risk of a miserable night with not much sleep followed by crashing the next day as soon as you can get into your room. If you do that, your body will be off schedule like it is after an overnight flight.

We took the sleeper train from Florence to Munich about 20 years ago and it was not a good choice. The 6 am arrival in Munich was a problem—our hotel would not accept dropped luggage at that hour, so we had to stash it in a locker and wander around until 10 am. There were drunks on the street near the train station; it was not pleasant. Turns out there was to be a football match later that day between Munich’s club and one from the UK, and the soccer hooligans were arriving in force. We had problems getting back to the station to collect our luggage because of the crowds pouring in.

I normally enjoy exploring a city in the quiet morning hours but not this time.

For a long journey like that, we prefer to break it up with an overnight in an attractive place along the way. But we are retired and have the time to do that.

I have done both (admittedly taking the train from Munich - Venice and flying the opposite direction on Air Dolomiti). I would say based on my experience you're better off flying given your proposed schedule, but if the train journey was during the day, the lovely mountain scenery is absolutely worth the day trip! So given your plans, I would say fly.

I love trains, but the idea of an overnight sleeper train has never appealed to me, so I've never taken one. It's hard for me to imagine I'd be able to sleep at all in one of these trains.

I love sleeper trains, and I've always gotten good rest on them. But that 6am arrival does sound rough.

There is also a direct train in the afternoon that does the trip in 6 1/2 hours. (The night train is slower on purpose). Not that much slower than going by plane, and you have the advantage of not needing to worry about extra. baggage fees, having the wrong stuff in your carry on, and you can actually enjoy the trip. That day time train would be my choice.

I like the day time train option too. There's also a 9:10a daytime train that connects in Verona and takes only a bit longer - I'm sure that's the one I would take instead of the afternoon train; even tough it's direct, it gets in so late. I usually hate afternoon departures; they seem to be a waste of that day, since I have to check out of my hotel and stow bags then have to be out of my room etc. Getting in 4:30 in the afternoon in Munich means I still have time to check in and unwind a little before dinner etc. instead of arriving at 8:30p, being tired and probably exhausted by the time I would be ready to eat dinner.

But, Venice Marco Polo is an easy airport even for international departures, so a flight to Munich would probably be very low stress too, other than needing to get up so early for the flight.

It's not just a one hour flight from Venice to Munich. It looks like the bus take 30 min. It also looks like the first bus from Venice in the morning would get you to the airport about 1½ hr before flight time, which should be about right time for what is really a local flight. If you need more time, then, you would have to take a later flight. So, it's 3 hours from P.le Roma to MUC. Fortunately there is an S-Bahn into Munich every 10 minutes (Ave), but, unfortunately, once you get to the S-Bahn station, it will be 45 -50 minutes to downtown Munich.

So, flying will take you over 4 hours compared to 9 hours by train. Plus the 4 hours is out of the useable day, not sleep time.

So, can you sleep on the train? In 11 nights on trains, I only once didn't get a good night's sleep, and that was when the train was 3 hour late leaving, and I naively thought they would make up the time, so I set my alarm according to the schedule arrival time in the early morning and then had to wait 3 hours in my compartment until I got to my destination.

Someone pointed out that there are 9 stops between Venice and Munich, but 5 are in the first 1H45, while they are picking up passenger. There are only 4 stops after 10:45.

I did it (private cabine) and I liked it a lot.

No problem in doing the night route, if I were going from Venice to Munich. Comparable night routes I've been on OeBB were from Vienna to Hamburg or to Berlin. The sleeper option is always the first option that sells out, which attest to the popularity of night trains.